Alpha blending processing whereby two images are composited together based on opacity degree of each of the pixels in each of the images is a known image processing technique (Refer to Patent Literature 1.). By using alpha blending processing to composite the foreground image onto a background image, an image can be created that makes the foreground image semi-transparent with respect to the background image.
When, for example, an image of an anime character (two-dimensional model) is a foreground image, alpha blending processing is used for fading in the character. When the character image is made semi-transparent with respect to a background image, the character image is composited onto the background image based on the opacity degree of the entire image of the character with respect to the background image.
When the character is wearing clothing, the character image is often an image in which an image of clothing is composited with an image of a body. Here, to display the semi-transparent image of the character, the image of the body is made semi-transparent and is composited onto the background image by using the alpha blending processing. Next, the image of the clothing in the foreground of image of the body is made semi-transparent and is composited. In such a case however, a semi-transparent image is generated in which the body that should be hidden shows through the clothing instead.
To prevent the body from showing through, first, the image of the body is overwritten with the image of the clothing and a semi-transparent character image is generated. Next, the generated character image is composited onto the background image through alpha blending processing.